I have not been much involved in Australian perfins so I cannot speak with certainty.
But the possibility exists for all perfined stamps to have been fed into the perforator machine in four directions while face up and 4 directions face down.
I do not know if every stamp was fed in every direction. It is possible but unlikely I would think. I should think a company mostly would appreciate latters or logos being upright in a normal position on stamps that went on correspondence to customers so as to maintain a good image in the eyes of others. I would anyway.
But that does not mean that mistakes did not happen, or the person operating the perforator was feeling ill or tired while perforating and thus made a slip up.
I almost started collecting perfins as the variety and possibilities are complex and vast. Especially Canadian perfins which have been considered to have so many fakes that it was almost impossible to get a 'true' perfin.
But this was only because there were many different dies of the perfins, different machines set in different ways.
There were fakes, indeed, as there are with anything to do with anything that catches the public's eye and that also command a premium in pricing at times, but not to the all encompassing extent that was previously believed years ago.
And who is to say that this variance in machines did not happen world wide? Further study is needed. A challenge and a puzzle, which I like.
This is a web site that has King George V perfins listed (for Australia and also for Worldwide) for stamps issued during the Silver Jubilee of KGV.http://www.philatel2.com/jubilee/id213.htm
The G / NSW perfin is only listed as rotated 90' left or right so this site would probably be grateful to know of one existing rotated 90' to the left and flipped over.